This is a very simple Login Mod for Minecraft Forge. I only made this mod because I couldn't find any other Login mods and Plugins don't work on Forge.
How the mod works:
When a Player (With a new Username) joins the world for the first time, they will have to set a password that they will need to use every time they rejoin with the same name.
This mod is made to prevent people on cracked servers from just logging onto others' accounts and grieving/stealing from them. If you have ever played on a bigger cracked server, then I'm sure you're at least a bit familiar with any Login Plugins out there.
This mod is not Serverside Only! This means every player on your server will have to have it installed!
Also, one last thing, I am not a professional in any way, shape, or form at coding. If you mess up the password, your game will crash. This is not intended, but It works.